The present invention relates to an electric switch assembly and more particularly to an electric switch assembly adaptable for locations of limited size.
In general, switches are used to connect and disconnect the flow of electric current between two or more wires or leads. This may be done by mechanical means in which conductive parts are brought into or out of contact inside the body of the switch. This bringing into contact of the conductive parts is effected by a part of the switch that may be referred to as the actuation member. The actuation member is thus the part of the switch that is responsive to the application of an external mechanical force to effect the bringing into or out of contact the conductive parts inside the switch in order to connect or disconnect the flow of electricity between two or more wires.
Many different types of switches have been made and designed having different sizes and different configurations for the both the internal conductive parts and for the actuation member in order to provide the desired operating characteristics for the particular application at hand. The operating characteristics of the switch may include the size of the actuation member, the amount of force necessary to effect movement of the actuation member, the range of movement of the actuation member (referred to herein as the "throw"), and the point in the throw of the actuation member at which switching action of the conductive parts takes place.
One such application is the use of switches as sensors. Because the actuation member of a switch operates by application of an external force, switches can be used as sensors to detect the movement or position of an object by locating the switch actuation member so that movement of the object operates the actuation member thereby operating the switch. Detection of the switch operation can thus be monitored remotely by measuring a voltage across or a current through leads connected to the switch. In this manner, switches may be used in combination with or as part of other devices or systems to effect control or operation thereof or to determine the status or location of components of the device or system.
A particular application in which a switch may be used as a sensor relates to an alarm to detect tampering with a cash box in a public telephone. In order to alert police or security personnel about an attempt of pilferage in progress, a switch may be located behind the cash box. (If the switch were on the side of the cash box, it could be defeated). The leads from the switch are connected to a remote location and monitored. Removal of the cash box moves the switch actuator thus operating the switch. This can be detected in the remote location by measurement of the voltage across or current through the leads. Removal of the cash box by maintenance or service personnel can be authorized by dialing in an access number via the telephone to inform the personnel at the remote location that removal of the cash box is authorized.
A problem presented in using a switch for this purpose is that there is little room available for the switch, i.e. approximately less than 1/4 inch. Any space that the switch occupies would detract from the volume available for the cash box. However, the switch to be used for this purpose should have a relatively large throw. Since the switch is intended to detect removal of the cash box which may be approximately 4 inches square, the actuation member should operate upon a movement of approximately an inch or more.
Switches have been made that are relatively small, i.e. that could fit behind the cash box. However, switches designed to be of such a miniature size tend to be expensive. Moreover, when switches are made to be of a smaller overall size, the size of the actuator as well as the amount of force required to effect switching and the "throw" of the actuator is typically reduced also. This presents a problem because even though the switch should be relatively small in a direction responsive to removal of the cash box, the switch should be responsive to only relatively large movements, e.g. an inch or more, of the cash box in that direction. With a typical switch of a size that is small enough to fit behind the cash box, a correspondingly small movement of the cash box in that direction could cause the switch to operate. Thus, small movements of the telephone unrelated to an attempt at pilferage could cause the switch to operate thus generating a false alarm. Moreover, if the switch actuation member has a small throw, the telephone cash box must have tolerances associated with its construction that correspond to those of the switch. This of course could lead to higher costs.
Another problem presented to the use of a switch for this purpose is that because pay telephones are often in an outdoor environment, there is a potential for moisture entering the switch and interfering with the operation thereof.
Accordingly, it is an object of the present invention to provide a switch that has a small profile relative to its actuation direction.
It is another object of the present invention to provide a switch that has a small profile relative to the throw of its actuation member.
It is yet another object of the present invention to provide a waterproof switch having a low profile.
It is still another object of the present invention to provide a waterproof switch that can be used in conjunction with a pay telephone to detect the removal therefrom of a cash box.